In message security, security information is inserted into messages so that it travels through the networking layers and arrives with the message at the message destination(s). Message security differs from transport layer security (which is discussed in the Security chapter of the J2EE 1.4 Tutorial) in that message security can be used to decouple message protection from message transport so that messages remain protected after transmission.
Web Services Security: SOAP Message Security (WS-Security) is an international standard for interoperable Web Services Security that was developed in OASIS by a collaboration of all the major providers of web services technology (including Sun Microsystems). WS-Security is a message security mechanism that uses XML Encryption and XML Digital Signature to secure web services messages sent over SOAP. The WS-Security specification defines the use of various security tokens including X.509 certificates, SAML assertions, and username/password tokens to authenticate and encrypt SOAP web services messages.
The WS-Security specification can be viewed at http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-soap-message-security-1.0.pdf.